A power supply is device that transfers power to a load to which the power supply is coupled wherein the power that is delivered has characteristics required by the load. Typically the power supply is coupled to a primary power source that has characteristics that are incompatible with the load to which it is coupled. The power supply makes the load compatible with its power source. A power supply is sometimes called a power converter and the process of delivering power from primary power source to load is termed “power conversion.”
Moreover, a power supply is a device that converts available power that has one set of characteristics to power that has another set of characteristics in order to meet specified load requirements. Typical applications of power supplies include the conversion of raw input power to controlled or stabilized voltage and/or current for the operation of electronic equipment.
A switched mode power supply is a power supply that provides the power supply function through low loss components such as capacitors, inductors, and transformers and the use of switches that assume one of two states (e.g., “on” or “off”). The advantage is that the switches dissipate very little power in either of these two states and power conversion can be accomplished with minimal power loss (which equates to high efficiency).
FIGS. 1 and 2 show conventional switched mode power supplies. FIG. 1 shows the circuit architecture employed when an op-amp is used as the circuit error amplifier, and FIG. 2 shows the circuit architecture employed when a GM amplifier is used as the circuit error amplifier. In the architectures shown in FIGS. 1 and 2 an opto-coupler is used in the feedback loop to avoid DC coupling between the input and the output stages of the device. These designs feature the use of voltage bias regulators and voltage bias resistors that have the effect of limiting the bandwidth of the circuit.
It should be appreciated that low bandwidth circuits such as these can cause the overall performance of the converter to be unstable. Such devices can require substantial and tedious bench testing from highly skilled personnel in order to stabilize the devices. In addition, conventional switched mode power supplies such as those shown in FIGS. 1 and 2 feature a significant parts count. In high volume applications the cost of producing such power supplies can be a competitive disadvantage. Moreover, the performance uncertainties that accompany their design contributes to time to market delays that places the manufacturers of such devices at a competitive disadvantage.